Roller conveyor

ABSTRACT

A roller conveyor in an as such known manner includes a plurality of driven rollers disposed in two parallel tracks. With each driven roller a drive motor is associated. From a first voltage source a first set of the driven rollers is supplied, wherein a second voltage source is provided, from which a further set of the driven rollers is supplied. This arrangement offers a high degree of redundancy in the event of the failure of individual components of the roller drive, thereby guaranteeing an emergency operation in such a situation.

RELATED APPLICATIONS

The present invention claims the benefit of the filing date of GermanPatent Application, Serial No. 10 2006 005 978.6, filed Feb. 8, 2006;the content of which is incorporated by reference herein.

This application also relates to concurrently filed U.S. patentapplication Ser. No. ______, entitled ROLLER CONVEYOR (Attorney DocketNo. OST-061317); and, ______, entitled SET OF ROLLER CONVEYORS (AttorneyDocket No. OST-061319)

TECHNICAL FIELD

The invention relates to a roller conveyor comprising a plurality ofdriven rollers disposed in two parallel tracks; a plurality of drivemotors for driving the rollers; and, at least one voltage source, fromwhich the drive motors are supplied.

BACKGROUND OF THE INVENTION

Roller conveyors are used to transport goods carriers such as e.g.pallets. In the automobile industry they are often used to transfervehicle bodies or parts of vehicle bodies between individual processingstations. The vehicle bodies are in said case fastened on so-calledskids. This term is used for transport racks that have two mutuallyparallel skid runners. During the conveying operation the skid runnersrest on rollers of the roller conveyor, which are disposed successivelyin conveying direction along two tracks. When the rollers are set inrotation, the skid with the vehicle body fastened thereon is fed inconveying direction, wherein it is sufficient to provide only some ofthe rollers with a rotary drive.

The roller conveyors of the initially described type, such as arecurrently known from the market, have only a single common voltagesource for all of the driven rollers. If this voltage source fails orsome other fault arises in the drive train, the article being conveyedcomes to a standstill and has to be removed possibly laboriously byhand. In the event of failure of a single driven roller, transport is nolonger possible over a considerable section corresponding to a rollerconveyor module, this generally leading likewise to an interruption ofconveying on the roller conveyor.

The present invention is provided to solve these and other problems.

SUMMARY OF THE INVENTION

An object of the present invention is to develop a roller conveyor ofthe initially described type in such a way that greater operationalreliability is achieved. This object is achieved according to theinvention in that: with each driven roller a drive motor is associated;a first voltage source is provided, from which a first set of the drivenrollers is supplied; and, at least one second voltage source isprovided, from which at least one further set of the driven rollers issupplied.

Thus, in accordance with the present invention, two measures are takenthat ensure a redundancy in the drive system of the driven rollers andhence provides fail safety. That is, the number of driven rollers isconsiderably increased compared to the background art so that in theevent of failure of a single driven roller, instead of a larger sectionof the roller conveyor being left without a drive, adjacent rollers aresubstantially able additionally to perform the function of the faileddriven roller. And also, the voltage source is provided at least induplicate so that, in the event of an electrical fault in the one drivetrain that leads to the failure of one set of driven rollers the otherdrive train remains operational and the driven rollers situated in thisdrive train may maintain at least one emergency conveying function.Admittedly, in such an emergency operating situation, because the numberof rollers is reduced it is not possible to achieve the sameaccelerations and speeds as during trouble-free operation. Theperformance of the remaining, operational driven rollers is howeversufficient to allow at least problem-free clearing of the rollerconveyor or to keep the roller conveyor in operation for a specifictime, albeit at a reduced conveying capacity.

Generally, it is sufficient to provide two voltage sources. It is onlyin extremely rare situations that both voltage sources develop faultssimultaneously.

Given the use of two voltage sources, the arrangement may be such thatone voltage source supplies all the driven rollers of the one track andthe other voltage source supplies all the driven rollers of the othertrack. In terms of cabling, this arrangement is particularly simple torealize. It does however have the drawback that the transport racks(skids) moving along the roller conveyor are driven at one side only.

It is therefore in principle also possible for rollers, which aresupplied from different voltage sources, to be disposed on the sametrack. In the event of failure of one set of driven rollers, there arenevertheless still driven rollers on both tracks. albeit at a greaterdistance apart from one one another. This variant of the roller conveyoraccording to the invention does however entail a slightly greater outlayfor cable installation.

The drive motors are advantageously low-voltage motors in particulard.c. low-voltage motors, because then the safety requirements are lowerand the semiconductor components less expensive.

For spatial and assembly reasons, it is preferable that the drive,motors are hub motors, which with the driven rollers form asub-assembly.

These and other objects and advantages will be made apparent from thefollowing brief description of the drawings and the detailed descriptionof the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a roller rail forming part of a rollerconveyor of the present invention;

FIG. 2 is a plan view-with partial electric cabling-showing a firstembodiment of the roller conveyor of the present invention; and,

FIG. 3 is a plan view-with partial electric cabling-showing a secondembodiment of a roller conveyor of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

While this invention is susceptible of embodiment in many differentforms, there is shown in the drawings and will herein be described indetail one or more embodiments with the understanding that the presentdisclosure is to be considered as an exemplification of the principlesof the invention and is not intended to limit the invention to theembodiments illustrated.

Reference is made first to FIG. 1, which shows a perspective view of aroller rail that is denoted as a whole by the reference character 10.The roller rail 10 comprises a longitudinal beam 12, which takes theform of a hollow section with a rectangular cross section. In thelongitudinal beam 12 two driven rollers 14 and two non-driven rollers 16are arranged alternately in longitudinal direction. The driven rollers14 are unprofiled and carry a high-friction coating. The non-drivenrollers 16 have a profile with wheel flanges on both sides. The wheelflanges effect lateral guidance of the runners of the skids to betransported.

Associated with each of the driven rollers 14 is a separate electric hubdrive motor, which with the rollers 14, forms in each case a compactdrive module and is not itself visible in the drawing.

As may be seen from FIG. 2, a roller conveyor 1 is composed of aplurality of roller rails 10 of the type illustrated in FIG. 1 byarranging these roller rails 10 into two parallel rows or “tracks”. Thedistance between the two tracks of roller rails 10 corresponds to thedistance between the runners of the skids that are to be conveyed alongthe roller conveyor 1.

The driven rollers 14 of the various roller rails 10 are supplied withelectrical energy in the following manner:

A line carrying the system voltage available at the site of installationof the roller conveyor is provided in FIG. 2 with the referencecharacter 18. Two direct voltage supply devices 20 a, 20 b are connectedto the supply line 18 and generate at in each case two outputs a lowdirect voltage of for example 24 V. One of these direct voltage supplydevices 20 a supplies all of the driven rollers 14 a in one of the twotracks of the roller conveyor 1, while the other of the two directvoltage supply devices 20 b supplies the driven rollers 14 b of thesecond track.

The one output of the direct voltage supply device 20 a is connected bya line 22 aa to all of the driven rollers 14 a that are situated, viewedfrom the direction of the direct voltage supply devices 20 a, 20 b, onone side thereof, while the second output of the direct voltage supplydevice 20 a is connected by a line 22 ab to all of the driven rollers 14a that are situated at the opposite side of the direct voltage supplydevices 20 a, 20 b.

In a corresponding manner, one of the two outputs of the direct voltagesupply device 20 b is connected by a line 22 ba to all of the drivenrollers 14 b of the second track of the roller conveyor 1 that aresituated, viewed from the direction of the direct voltage supply devices20 a, 20 b, on one side thereof, while the second output of the directvoltage supply device 20 b via a line 22 bb supplies all of the drivenrollers 14 b of the, in FIG. 2, right track that are situated on theopposite side of the direct voltage supply devices 20 a, 20 b. The useof hub drive motors operated with a low voltage offers a whole range ofadvantages:

The foremost of these is the fact that the safety requirements are thenconsiderably lower than would be the case with drive technologyoperating with full system voltage. This leads to savings in terms ofinstallation technology. Furthermore, the semiconductor components thatare used in the direct voltage supply devices 20 a, 20 b and in thecontrol components of the driven rollers 14 are considerably lessexpensive. The printed conductors on the printed-circuit boards, for theprevention of voltage flashovers, do not have to maintain such largesafety distances from one another, with the result that theprinted-circuit boards themselves are reduced in size and may beintegrated without difficulty e.g. into a compact drive module withdriven roller 14 and corresponding control components. The drivenrollers 14 may be used in a braking operation as generators, with theresult that electrical energy may be saved. Finally, lower losses occurin low voltage circuit components, with the result that once more anenergy-saving effect arises and only small cooling surfaces arerequired.

As the direct voltage supply devices 20 a, 20 b are provided induplicate, the roller conveyor 1 has an “emergency operation property”for the eventuality of a fault occurring in one of the two drive trainsthat are supplied by the direct voltage supply devices 20 a, 20 b. Therespective intact “drive train” may then perform the entire drivefunction for a specific time, albeit at the cost of specific cutbacks inacceleration and speed.

The embodiment of a roller conveyor 101 illustrated in FIG. 3 is verysimilar to the embodiment described above with reference to FIG. 2.Corresponding parts are therefore denoted by the same referencecharacters plus 100. The roller conveyor 101 of FIG. 3 is also composedof a plurality of roller rails 110, of the type illustrated in FIG. 1.To this extent, the mechanical construction of the embodiment of FIG. 3is no different from that of FIG. 2. However, the various driven rollers114 a, 114 b in the two tracks of the roller conveyor 101 are suppliedin a different manner.

As may be seen from FIG. 3, along both tracks of the roller conveyor 101of FIG. 3 there extend two lines 122 aa, 122 ba and 122 ab, 122 bbrespectively, which carry a low direct voltage. The supply lines 122 aaand 122 ab are both connected to one of the two direct voltage supplydevices 120 a, while the two supply lines 122 ba and 122 bb areconnected to the second direct voltage supply device 120 b.

As FIG. 3 reveals, all of the driven rollers 114 a of the left track ofthe roller conveyor 101 are connected alternately, on the one hand, tothe supply line 122 aa and, on the other hand, to the supply line 122ba. The result of this is that in each of the roller rails 110 there isin each case one driven roller 114 that is supplied from the one directvoltage supply device 120 a and one driven roller 114 that is suppliedfrom the other direct voltage supply device 120 b.

The conditions in the, in FIG. 3, right track of the roller conveyor 101are similar. Here too, the driven rollers 114 are connected alternatelyto the line 122 ab and the line 122 bb, ultimately therefore alternatelyto the direct voltage supply device 120 a and the direct voltage supplydevice 120 b .

In the embodiment of the roller conveyor 101 in FIG. 3, in the event offailure of one of the electric “drive trains”, for example one of thetwo direct voltage supply devices 120 a, 120 b, then as in theembodiment of FIG. 2 an emergency operation of the roller conveyor 101is possible. However, whereas in the embodiment of FIG. 2 there aredriving forces exclusively in one track of the roller conveyor 1, in theembodiment of FIG. 3 even in the event of failure of one “drive train”there are still driven rollers 114 in both tracks. This promotes thedirectional stability of the skids during emergency operation.

Control of the various driven rollers 14, 114 is effected via anindustry-standard bus system.

It should be emphasized that the above-described embodiments of thepresent invention, particularly, any “preferred” embodiments, arepossible examples of implementations. merely set forth for a clearunderstanding of the principles of the invention. Many variations andmodifications may be made to the above-described embodiments of theinvention without substantially departing from the spirit and principlesof the invention. All such modifications are intended to be includedherein within the scope of this disclosure and the present invention,and protected by the following claims.

1. A roller conveyor comprising: a plurality of driven rollers disposedin two parallel tracks; a plurality of drive motors for driving therollers; at least one voltage source, from which the drive motors aresupplied; wherein with each driven roller a drive motor is associated; afirst voltage source is provided, from which a first set of the drivenrollers is supplied; and, at least one further voltage source isprovided, from which at least one further set of the driven rollers issupplied.
 2. The roller conveyor of claim 1, wherein voltage sources areprovided.
 3. The roller conveyor of claim 2, wherein one voltage sourcesupplies all of the driven rollers of one of the parallel tracks and theother voltage source supplies all of the driven rollers of another ofthe parallel tracks.
 4. The roller conveyor of claim 1, wherein drivenrollers supplied from different voltage sources are disposed on the sametrack.
 5. The roller conveyor of claim 2, wherein driven rollerssupplied from different voltage sources are disposed on the same track.6. The roller conveyor of claim 1, wherein the drive motors are lowvoltage motors.
 7. The roller conveyor of claim 6, wherein the drivemotors are low voltage motors.
 8. The roller conveyor of claim 2,wherein the drive motors are low voltage motors.
 9. The roller conveyorof claim 3, wherein the drive motors are low voltage motors.
 10. Theroller conveyor of claim 4, wherein the drive motors are low voltagemotors.
 11. The roller conveyor of claim 5, wherein the drive motors arelow voltage motors.
 12. The roller conveyor of claim 6, wherein thedrive motors are low voltage motors.
 13. The roller conveyor of claim 7,wherein the drive motors are low voltage motors.
 14. The roller conveyorof claim 2, wherein the drive motors are hub motors, which with thedriven rollers form a sub-assembly.
 15. The roller conveyor of claim 3,wherein the drive motors are hub motors, which with the driven rollersform a sub-assembly.
 16. The roller conveyor of claim 4, wherein thedrive motors are hub motors, which with the driven rollers form asub-assembly.
 17. The roller conveyor of claim 5, wherein the drivemotors are hub motors, which with the driven rollers form asub-assembly.
 18. The roller conveyor of claim 6, wherein the drivemotors are hub motors, which with the driven rollers form asub-assembly.
 19. The roller conveyor of claim 7, wherein the drivemotors are hub motors, which with the driven rollers form asub-assembly.